2. Description of the Prior Art
Water and lighter hydrocarbon fuels (gasoline and diesel) do not stay mixed long enough for combustion purposes and several strategies have been employed to achieve sufficient emulsion stability. U.S. Pat. No. 6,607,566 Coleman teaches using a small quantity of emulsifying agent and significant mechanical agitation to create fuel macro-emulsions (having water droplets greater than 1.0 microns diameter). U.S. Pat. No. 3,876,391 McCoy teaches fuel micro-emulsions (having water droplets smaller than 0.1 microns diameter) using significantly more emulsifying agents and less mechanical agitation.
Prior art water levels of 10,000 to 400,000 parts per million (“ppm”) in the fuel is generally accepted as necessary to achieve any worthwhile improvement in combustion.
However, in order to achieve even short term fuel emulsion stability at these “high” water levels, significantly large quantities of “expensive” emulsifying surfactants are required (typically 5,000 to 200,000 ppm). This surfactant expense always makes the cost/benefit ratio of this type of high water content fuel emulsion unsuitable for regular commercial applications. Typical of all this group of patents is U.S. Pat. No. 4,744,796 Hazbun.
U.S. Pat. No. 4,396,400 Grangette claims 1,000 ppm of emulsified water (together with 500 ppm of surfactant) gives the optimum improvement. Again, using 500 ppm of surfactant would still make this fuel too expensive for most commercial applications.
Grangette also discloses that it is possible to produce “ultra-low” water content fuel emulsions by adding 100 ppm of water, but employing only 25 ppm of a single “crude” surfactant. With so much water and so little surfactant, the resulting fuel emulsion would not be stable enough for commercial applications. Grangette failed to realize that any ultra low water content fuel emulsion (about 100 ppm added water) always requires significantly more “crude” surfactant than added water in order to remain stable over the required lifetime of the fuel (extra surfactants are required to emulsify the 50 to 100 ppm dissolved water typically present in all commercially available liquid hydrocarbon fuels). This requirement has never been recognized and used by any prior art.